Where a sensor senses an image of a geographic environment, automatic target recognition ("ATR") is assisted by relating the sensor to the geographic environment. The sensor can be either a passive sensor such as a FLIR sensor or an active sensor such as a LADAR or RADAR sensor. A passive sensor emits relatively little energy and primarily detects energy, such as black body radiation, emitted by a source other than the system to which the passive sensor belongs. A passive sensor is useful for measuring a velocity perpendicular to the sensor's line of sight, such as a velocity of a target object along a horizon between a sky and a planet's surface.
By comparison, an active sensor emits significant energy and primarily detects a reflection of its own emitted energy from the geographic environment. Active sensors are useful for typical "ranging" systems that determine a three-dimensional model of a geographic environment's topography. For example, an active sensor is useful for measuring a range of a target object away from the sensor, according to the travel time of a reflected energy pulse. Also, an active sensor is useful for measuring a velocity parallel to the sensor's line of sight, such as a velocity of a target object toward or away from the sensor, according to a frequency change of the reflected energy pulse.
Although an active sensor is practical for a diverse range of environmental conditions, a passive sensor advantageously consumes less power and is more covert. Previous techniques typically fail to relate a position and attitude of a passive sensor to a geographic environment. Accordingly, previous techniques typically fail to sufficiently reduce uncertainties concerning a target object's appearance in an image sensed by a passive sensor.
Thus, a need has arisen for a method and system for relating a passive sensor to a geographic environment, in which a position and attitude of the passive sensor are related to the geographic environment. Also, a need has arisen for a method and system for relating a passive sensor to a geographic environment, in which uncertainties are reduced concerning a target object's appearance in an image sensed by the passive sensor.